filter

Abstract

The utility model relates to a kind of filter, including switch antenna circuit, wave trap circuit, π type circuit and signal transmitting circuit;The output end of signal transmitting circuit is electrically connected with the input end of π type circuit, the output end of π type circuit is electrically connected with the input end of wave trap circuit, the output end of wave trap circuit is electrically connected with the input end of switch antenna circuit.By the frequency selection characteristic of reasonable design π type circuit and the stopband characteristic of wave trap circuit, according to the filter of the utility model embodiment, out-of-band interference and high-order harmonic radiation can be effectively suppressed, impedance matching in signal transmission process is optimized to reduce reflection loss, while supporting switch antenna circuit dynamic switching filtering path or antenna port, adapt to multi-band communication scene, improve signal purity and power transmission efficiency, meet the high anti-interference demand of wireless communication base station, radio frequency transceiver module and the like scene.

Description

Technical Field

[0001] This utility model relates to the field of wireless communication technology, and in particular to a filter. Background Technology

[0002] Existing designs for communication module transmission links typically employ SAW (Surface Acoustic Wave Filter), LPF (Low-Pass Filter), or BPF (Band-Pass Filter). The signal transmission path is as follows: after the signal is output from the power amplifier (PA), it first passes through the impedance matching circuit before the filter, then is filtered again, subsequently transmitted through the matching circuit at the back end, and finally transmitted by the antenna via a front-end switch. However, this approach has significant drawbacks. The overall link involves a large number of components, resulting in cumbersome assembly processes, reduced production efficiency, and increased difficulty in troubleshooting. Therefore, innovative design solutions to optimize the transmission link are urgently needed. Utility Model Content

[0003] To address the shortcomings of existing technologies, this utility model proposes a filter, including a switching antenna circuit, a notch filter circuit, a π-type circuit, and a signal transmission circuit;

[0004] The output terminal of the signal transmitting circuit is electrically connected to the input terminal of the π-type circuit, the output terminal of the π-type circuit is electrically connected to the input terminal of the notch filter circuit, and the output terminal of the notch filter circuit is electrically connected to the input terminal of the switching antenna circuit.

[0005] In one embodiment of the utility model, a first capacitor is connected in series between the π-type circuit and the notch filter circuit.

[0006] In one embodiment of the utility model, the π-type circuit includes a first inductor, a second capacitor, and a third capacitor. The second capacitor and the third capacitor are connected in parallel across the two ends of the first inductor, and the first inductor is electrically connected to the first capacitor.

[0007] In one embodiment of the utility model, the notch filter circuit includes a second inductor and a fourth capacitor, the fourth capacitor being connected in parallel with the second inductor, and the second inductor being electrically connected with the first capacitor.

[0008] In one embodiment of the utility model, the signal transmitting circuit includes a PA power amplifier chip, and port 14 of the PA power amplifier chip is electrically connected to a first inductor.

[0009] In one embodiment of the utility model, the switching antenna circuit includes an SP8T antenna switching chip, an antenna matching circuit, a control signal circuit, and a power supply circuit;

[0010] The antenna matching circuit, control signal circuit, and power supply circuit are electrically connected to the SP8T antenna switch chip.

[0011] In one embodiment of the utility model, port 10 of the SP8T antenna switch chip is electrically connected to the output terminal of the notch filter circuit, and multiple signal output terminals of the SP8T antenna switch chip are electrically connected to the corresponding antennas.

[0012] In one embodiment of the utility model, the antenna matching circuit includes a third inductor, a fourth inductor, and a fifth capacitor. The fourth inductor and the fifth capacitor are connected in parallel across the two ends of the third inductor, and the third inductor is electrically connected to port 13 of the SP8T antenna switch chip.

[0013] In one embodiment of the utility model, the control signal circuit includes a first line, a second line, and a third line. The first line is electrically connected to port 5 of the SP8T antenna switch chip, the second line is electrically connected to port 6 of the SP8T antenna switch chip, and the third line is electrically connected to port 7 of the SP8T antenna switch chip.

[0014] In one embodiment of the utility model, the power supply line is electrically connected to port 4 of the SP8T antenna switch chip.

[0015] The beneficial effects of this utility model are:

[0016] In this filter, the signal transmitting circuit, π-type circuit, notch filter circuit, and switching antenna circuit are sequentially electrically connected to form a complete signal processing chain. The output of the signal transmitting circuit is connected to the π-type circuit, which, through its inductor-capacitor network, synchronously achieves precise impedance matching, reduces signal reflection loss, improves power transmission efficiency, and attenuates out-of-band harmonics and other spurious signals in advance, thus purifying signal quality. The output of the π-type circuit is connected to the notch filter circuit, constructing a relay mechanism of "wideband filtering + narrowband suppression." The π-type circuit is responsible for overall spectrum shaping, while the notch filter circuit focuses on specific interference frequencies for precise blocking, solving the defects of single-topology filtering and ensuring signal bandwidth flatness and anti-interference. The output of the notch filter circuit is connected to the switching antenna circuit, allowing the filtered signal to be flexibly distributed to different antenna channels, adapting to the complex requirements of multi-antenna architectures, replacing traditional redundant solutions, reducing PCB area, reducing insertion loss, and helping equipment achieve better performance in multi-mode multi-frequency communication.

[0017] Other features and aspects of the present invention will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0018] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of the present invention together with the specification and serve to explain the principles of the present invention.

[0019] Figure 1 The diagram shows the main circuit structure of the filter according to an embodiment of the present invention;

[0020] Figure 2 The diagram shows the filter circuit of an embodiment of the present invention.

[0021] Figure 3 This diagram shows the switching antenna circuit of the filter according to an embodiment of the present invention;

[0022] Figure 4 This diagram shows the PA transmitter circuit of the filter according to an embodiment of the present invention; Detailed Implementation

[0023] Various exemplary embodiments, features, and aspects of the present invention will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0024] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0026] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0027] Furthermore, to better illustrate this utility model, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this utility model can be implemented even without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail, in order to highlight the main points of this utility model.

[0028] The filter of this invention is an integrated radio frequency front-end filter circuit. It is used in the field of wireless communication technology to optimize the signal quality of the transmission link, suppress interference, reduce the number and size of components, and reduce costs.

[0029] Specific references Figures 1-4 As a specific embodiment of the filter of this utility model, the filter includes: a switching antenna circuit 110, a notch filter circuit 120, a π-type circuit and a signal transmission circuit. The filter is mainly composed of the switching antenna circuit 110, the notch filter circuit 120, the π-type circuit 130 and the signal transmission circuit 140.

[0030] The output of the signal transmitting circuit 140 is electrically connected to the input of the π-type circuit 130, the output of the π-type circuit 130 is electrically connected to the input of the notch filter circuit 120, and the output of the notch filter circuit 120 is electrically connected to the input of the switching antenna circuit 110. The signal transmission path from the transmitter to the antenna follows the logic chain of "power amplification → primary filtering → interference suppression → antenna switching and matching": the power amplifier in the signal transmitting circuit 140 first amplifies the weak radio frequency signal to a sufficient strength, and the output is connected to the π-type circuit 130 for impedance matching and primary filtering to optimize the signal spectrum characteristics; the signal output from the π-type circuit 130 is directly connected in series to the notch filter circuit 120, which deeply attenuates interference at specific frequencies through the LC (Inductor-Capacitor) resonance principle; the clean signal after notch filtering enters the switching antenna circuit 110, and the SP8T switching chip switches different antenna ports according to the control signal. The matching network further optimizes the impedance matching between the antenna and the front-end circuit, ultimately achieving efficient signal radiation. This four-stage cascaded architecture, through integrated design and parameter coordination, improves the filtering performance and anti-interference capability of the entire link while reducing the number of components.

[0031] Furthermore, such as Figure 1 As shown, the complete path of the signal from transmission to antenna radiation is as follows: the signal transmitting circuit 140 serves as the starting point, outputting the amplified RF signal to the input of the π-type circuit 130 to complete preliminary impedance matching and filtering; the output of the π-type circuit 130 is connected in series to the notch circuit 120 to specifically filter out interference at a particular frequency; the clean signal output from the notch circuit 120 is connected to the input of the switching antenna circuit 110, which switches different antenna paths through a "switch," and finally the antenna completes the signal radiation. This connection relationship forms a clear signal flow in the figure: PA power amplification → π-type matching → notch matching → switch → antenna, realizing a complete functional chain of "signal amplification → primary filtering → interference suppression → antenna gating." The modules work together, which not only reduces the number of discrete components but also improves signal transmission efficiency and anti-interference capability through multi-stage matching optimization.

[0032] In this embodiment, a first capacitor C0 is connected in series between the π-type circuit 130 and the notch filter circuit 120. This first capacitor C0 further adjusts the impedance characteristics of the circuit, improves the signal coupling effect between the two stages, and reduces reflection loss during signal transmission. Simultaneously, by appropriately selecting the capacitance value, phase compensation can be performed on signals of specific frequencies, resulting in a smoother frequency response for the entire filtering link and optimized filtering performance.

[0033] In this embodiment, the π-type circuit 130 includes a first inductor L1, a second capacitor C1, and a third capacitor C2. The second capacitor C1 and the third capacitor C2 are connected in parallel across the first inductor L1, and the first inductor L1 is electrically connected to the first capacitor C0. The π-type circuit 130, composed of the first inductor L1, the second capacitor C1, and the third capacitor C2, with the second capacitor C1 and the third capacitor C2 connected in parallel across the first inductor L1, and the first inductor L1 electrically connected to the first capacitor C0, is primarily used for preliminary filtering and impedance matching of the signal output from the signal transmitting circuit 140. The first inductor L1 and the parallel capacitors form an LC (Inductor-Capacitor) filter network. According to design requirements, by adjusting the parameters of the inductor and capacitor, signals in specific frequency bands can be selectively passed or attenuated, while simultaneously adjusting the output impedance of the signal source to a suitable value to match the input impedance of the subsequent notch filter circuit 120.

[0034] In this embodiment, the notch filter circuit 120 includes a second inductor L2 and a fourth capacitor C9. The fourth capacitor C9 is connected in parallel with the second inductor L2, and the second inductor L2 is electrically connected to the first capacitor C0. The notch filter circuit 120 includes a second inductor L2 and a fourth capacitor C9 connected in parallel, and then the second inductor L2 and the first capacitor C0 are connected in series. This notch filter circuit 120 suppresses interference signals of specific frequencies. When certain frequencies in the signal coincide with the resonant frequency of the LC (inductor-capacitor) parallel resonant circuit composed of the second inductor L2 and the fourth capacitor C9, the circuit presents high impedance, preventing signals of that frequency from passing through, thereby achieving the purpose of filtering out interference signals of specific frequencies and improving the purity of the output signal.

[0035] Further such as Figure 2As shown, in the signal transmission path, the signal transmitted by PA first enters the π-type circuit 130. The π-type circuit 130 consists of a first inductor L1, a second capacitor C1, and a third capacitor C2. The second capacitor C1 and the third capacitor C2 are connected in parallel across the first inductor L1, completing impedance matching and preliminary filtering. The notch filter circuit 120 consists of a second inductor L2 and a fourth capacitor C9. The fourth capacitor C9 is connected in parallel with the second inductor L2. A first capacitor C0 is connected in series between the π-type circuit 130 and the notch filter circuit 120. The first capacitor C0 can further optimize impedance matching and compensate for signal phase, allowing the signal to be transmitted more smoothly from the π-type circuit 130 to the notch filter circuit 120. The notch filter circuit 120 then uses the parallel resonance characteristics of the second inductor L2 and the fourth capacitor C9 to suppress specific interference frequencies. The various circuit components and connection methods cooperate with each other to achieve filtering and anti-interference processing of the transmitted signal, thereby improving signal quality.

[0036] Furthermore, the CLC topology forms a π-type network (components include a second capacitor C1, a first inductor L1, and a third capacitor C2) for impedance matching and harmonic suppression. A reserved first capacitor C0 ensures flexibility in circuit debugging. Then, an LC resonant circuit (components include a fourth capacitor C9 and a second inductor L2) and a microstrip line coupling form a notch circuit for further harmonic suppression, achieving deep attenuation at specific frequency points (such as second / third harmonics), suppressing PA nonlinear distortion products, and enabling the product to achieve superior emission performance. The values ​​of the second capacitor C1, first inductor L1, third capacitor C2, fourth capacitor C9, and second inductor L2 can be adjusted according to the required frequency band to meet the suppression and filtering requirements of the corresponding frequency points.

[0037] In this embodiment, the signal transmitting circuit 140 includes a power amplifier (PA) chip. Port 14 of the PA chip is electrically connected to a first inductor L1. The PA chip amplifies the weak input radio frequency signal to provide sufficient power to meet the requirements of wireless communication. The PA chip of the signal transmitting circuit 140 establishes a radio frequency output path through port 14 and the first inductor L1. In practical applications, the PA chip amplifies the weak signal emitted by the system to a sufficient power level.

[0038] Furthermore, such as Figure 4As shown, the signal transmitting circuit 140 is based on the PA power amplifier chip XP5733-12. It has multiple signal inputs (such as TX_HB_K, X_MB, TX_LB_K, etc.). After being processed by a filtering and matching network composed of capacitors (C1620, C1632, etc.) and inductors (C1633, C1639, etc.), the signals are connected to the chip port. At the same time, the PA power amplifier chip is connected to the power supply (VDD18_RF, VBAT, etc.) and control signal (RFEE_CM, RFEE_DAT) lines, which can amplify and condition the transmitted signals of different frequency bands, providing the required radio frequency signals for subsequent filtering and antenna transmission stages. All components work together to ensure the power, spectrum and other performance of the transmitted signal.

[0039] In this embodiment, the switching antenna circuit 110 includes an SP8T (single-pole eight-throw) antenna switch chip, an antenna matching circuit, a control signal circuit, and a power supply circuit. The antenna matching circuit, control signal circuit, and power supply circuit are electrically connected to the SP8T (single-pole eight-throw) antenna switch chip. The switching antenna circuit 110 is composed of the SP8T antenna switch chip, antenna matching circuit, control signal circuit, and power supply circuit, and all three are connected to the SP8T (single-pole eight-throw) antenna switch chip. The SP8T (single-pole eight-throw) antenna switch chip, as the core component, can switch between multiple antenna ports according to the control commands input from the control signal line, thus enabling the selection of different antennas. The antenna matching circuit optimizes the impedance matching between the antenna and the SP8T (single-pole eight-throw) antenna switch chip, improving signal transmission efficiency; the control signal line transmits control signals to control the operating state of the antenna switch chip; and the power supply line provides a stable operating voltage to the SP8T (single-pole eight-throw) antenna switch chip.

[0040] In this embodiment, port 10 of the SP8T (single-pole eight-throw) antenna switch chip is electrically connected to the output of the notch filter circuit 120. Multiple signal outputs of the SP8T antenna switch chip are electrically connected to their respective antennas. The signal filtered by the notch filter circuit 120 enters the SP8T antenna switch chip. The chip switches the signal to the designated antenna port according to the control signal, realizing signal transmission from the circuit to the antenna, thereby meeting the antenna selection and signal transmission requirements of multi-antenna systems in different communication scenarios.

[0041] In this embodiment, the antenna matching circuit includes a third inductor C1801, a fourth inductor L1801, and a fifth capacitor L1802. The fourth inductor L1801 and the fifth capacitor L1802 are connected in parallel across the third inductor C1801. The third inductor C1801 is electrically connected to port 13 of the SP8T (single-pole eight-throw) antenna switch chip. The antenna matching circuit is composed of the third inductor C1801, the fourth inductor L1801, and the fifth capacitor L1802, wherein the fourth inductor L1801 and the fifth capacitor L1802 are connected in parallel across the third inductor C1801, and the third inductor C1801 is connected to port 13 of the SP8T (single-pole eight-throw) antenna switch chip. The function of this antenna matching circuit is to adjust the impedance between the antenna and the SP8T (single-pole eight-throw) antenna switch chip, so that the input impedance of the antenna matches the output impedance of the front-end circuit, reducing signal reflection at the antenna end and improving signal radiation efficiency. By precisely calculating and adjusting the parameters of the three components, a good impedance matching effect can be achieved within the target frequency band.

[0042] In this embodiment, the control signal circuit includes a first line, a second line, and a third line. The first line is electrically connected to port 5 of the SP8T (single-pole eight-throw) antenna switch chip, the second line is electrically connected to port 6 of the SP8T (single-pole eight-throw) antenna switch chip, and the third line is electrically connected to port 7 of the SP8T (single-pole eight-throw) antenna switch chip. These three lines are used to transmit control signals, which can be digital signals from a microcontroller or other control unit. By changing the signal level combination on the three lines, the on / off state of the internal switch of the SP8T (single-pole eight-throw) antenna switch chip can be controlled, thereby enabling the selection and switching of different antenna ports and meeting the diverse requirements of the system for antenna operating modes.

[0043] In this embodiment, the power supply line is electrically connected to port 4 of the SP8T (single-pole eight-throw) antenna switch chip, providing a stable operating power supply to the chip. Through reasonable power filtering and voltage regulation design, the power supply line ensures stable voltage input to the chip, preventing abnormal chip operation due to power fluctuations. Simultaneously, the power supply line can also provide sufficient current according to the chip's power consumption requirements, ensuring that the SP8T (single-pole eight-throw) antenna switch chip can reliably perform antenna switching and other operations.

[0044] Furthermore, such as Figure 3As shown, the switching antenna circuit 110 uses the SP8T (single-pole eight-throw) antenna switch chip CAN1418R as its core. The antenna matching circuit consists of a third inductor C1801, a fourth inductor L1801, and a fifth capacitor L1802. The fourth inductor L1801 and the fifth capacitor L1802 are connected in parallel in the link of the third inductor C1801 to achieve signal impedance matching. The control signal lines (CTRL_SW_V3, CTRL_SW_V2, and CTRL_SW_V1, corresponding to the first, second, and third lines, respectively) are connected to ports 5, 6, and 7 of the SP8T (single-pole eight-throw) antenna switch chip to control the switching of the antenna channel. The power supply line is connected to port 4 of the SP8T (single-pole eight-throw) antenna switch chip and is powered by a VLDO6_2V8 power supply. The SP8T (single-pole eight-throw) antenna switch chip uses port 13 (ANT) as a signal input terminal to receive the output signal of the notch filter circuit 120. Ports 3, 6, 9, 10, 1, 11, 14, and 12 (RF1-RF8) serve as multiple signal output terminals, which are respectively connected to antennas such as B3_TRM, TDD_RX_ANT, B1_TPM, B34 / 39_TX_ANT, B6_TRM, B40_TRX_ANT, and B8_TRM. Each part of the circuit works in conjunction with the SP8T (single-pole eight-throw) antenna switch chip, and the switching antenna circuit 110 can transmit the signal from the filter circuit.

[0045] The filter provided by this utility model includes a switching antenna circuit, a notch filter circuit, a π-type circuit, and a signal transmitting circuit. The output terminal of the signal transmitting circuit is electrically connected to the input terminal of the π-type circuit. The output terminal of the π-type circuit is connected in series with the input terminal of the notch filter circuit via a first capacitor. The output terminal of the notch filter circuit is electrically connected to the input terminal of the switching antenna circuit. The π-type circuit consists of a first inductor and two capacitors connected in parallel across it. The notch filter circuit consists of a second inductor and a fourth capacitor connected in parallel. The signal transmitting circuit includes a PA power amplifier chip, and its port 14 is electrically connected to the first inductor. The switching antenna circuit integrates an SP8T antenna switch chip, and its port 10 is connected to the output terminal of the notch filter circuit. The antenna matching circuit consists of a third inductor and a fourth inductor and a fifth capacitor connected in parallel across it, and is connected to the chip port 13. The control signal circuit is connected to the chip ports 5, 6, and 7 via three lines, and the power supply circuit is connected to port 4. This filter can effectively suppress out-of-band interference and improve signal purity through cascaded filtering of π-type circuits and notch circuits, combined with multi-channel switching of antenna switches and impedance optimization of matching circuits, while realizing efficient transmission of multi-band signals and antenna switching control.

[0046] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A filter, characterized in that, This includes a switching antenna circuit, a notch filter circuit, a π-type circuit, and a signal transmitting circuit; The output terminal of the signal transmitting circuit is electrically connected to the input terminal of the π-type circuit, the output terminal of the π-type circuit is electrically connected to the input terminal of the notch filter circuit, and the output terminal of the notch filter circuit is electrically connected to the input terminal of the switching antenna circuit.

2. The filter according to claim 1, characterized in that, A first capacitor is connected in series between the π-type circuit and the notch circuit.

3. The filter according to claim 2, characterized in that, The π-type circuit includes a first inductor, a second capacitor, and a third capacitor. The second and third capacitors are connected in parallel across the two ends of the first inductor, and the first inductor is electrically connected to the first capacitor.

4. The filter according to claim 3, characterized in that, The notch filter circuit includes a second inductor and a fourth capacitor. The fourth capacitor is connected in parallel with the second inductor, and the second inductor is electrically connected to the first capacitor.

5. The filter according to claim 3, characterized in that, The signal transmitting circuit includes a PA power amplifier chip, and port 14 of the PA power amplifier chip is electrically connected to the first inductor.

6. The filter according to claim 4, characterized in that, The switching antenna circuit includes an SP8T antenna switching chip, an antenna matching circuit, a control signal circuit, and a power supply circuit. The antenna matching circuit, the control signal circuit, and the power supply circuit are electrically connected to the SP8T antenna switch chip.

7. The filter according to claim 6, characterized in that, Port 10 of the SP8T antenna switch chip is electrically connected to the output terminal of the notch filter circuit, and multiple signal output terminals of the SP8T antenna switch chip are electrically connected to the corresponding antennas.

8. The filter according to claim 6, characterized in that, The antenna matching circuit includes a third inductor, a fourth inductor, and a fifth capacitor. The fourth inductor and the fifth capacitor are connected in parallel across the three ends of the third inductor. The third inductor is electrically connected to port 13 of the SP8T antenna switch chip.

9. The filter according to claim 6, characterized in that, The control signal circuit includes a first line, a second line, and a third line. The first line is electrically connected to port 5 of the SP8T antenna switch chip, the second line is electrically connected to port 6 of the SP8T antenna switch chip, and the third line is electrically connected to port 7 of the SP8T antenna switch chip.

10. The filter according to claim 6, characterized in that, The power supply circuit is electrically connected to port 4 of the SP8T antenna switch chip.

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